Directional solidification furnaces are used, for example, to produce multi-crystalline silicon ingots. These furnaces have a crucible into which raw poly-crystalline silicon is placed. The crucible is supported by a structure that adds structural rigidity to the crucible. The crucible is disposed within a containment vessel that forms part of the furnace and seals the crucible from the ambient environment.
During use, the raw silicon is melted and then cooled at a controlled rate to achieve directional solidification within the resulting ingot. The controlled rate of cooling is established by any combination of reducing the amount of heat applied by the heaters, movement of or opening of insulation surrounding the crucible, and/or the circulation of a cooling medium through a heat exchanger disposed adjacent the crucible and/or the crucible support. The ingot solidifies in the region closest to the cooler side of the crucible and proceeds in a direction away from the cooler side of the crucible.
The size of silicon ingots produced in these furnaces has been increasing in order to improve efficiency and reduce the cost required to produce the ingots. However, previous attempts to increase the mass of the silicon ingots over about 600 kg have proved unsuccessful for a variety of reasons. There exists a need for a silicon ingot having greater mass (e.g., greater than about 600 kg) and furnaces capable of producing these larger ingots.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.